This invention relates to methods, compositions and kits for detecting the presence and/or amounts of amphetamine and/or methamphetamine in samples suspected of containing the same. In particular, the invention relates to bivalent hapten conjugates comprising an amphetamine moiety and a methamphetamine moiety. The conjugate may be employed in assays for amphetamine and/or methamphetamine.
The clinical diagnostic field has seen a broad expansion in recent years, both as to the variety of materials of interest that may be readily and accurately determined, as well as the methods for the determination. Over the last decade, testing for drugs of abuse has become commonplace. This testing is not only for the monitoring of criminal offenders and drug addicts, but employers also use it for the screening of workers. In recent years, immunoassays based on the reaction of an antibody with an antigen have been extensively investigated for this purpose.
Typically, immunoassays employ an antibody whose structure recognizes an analyte in a specific manner. The immunoassay is conducted with a signal producing system that produces a detectible change in signal upon binding of the analyte to the antibody. Accordingly, when testing for an analyte in a sample, a detectible change in signal from that produced with a negative sample of a calibrator is taken as a positive result for the presence of that analyte in the sample.
Amphetamine and methamphetamine stimulate the central nervous system and have been used medicinally to treat hypotension, narcolepsy and obesity. Because of their stimulating effects, the drugs and derivatives have been abused. As a result, assays for the detection of amphetamine and/or methamphetamine in samples are of interest.
There is a problem when the aforementioned assay techniques are employed to assay for amphetamines in a sample suspected of containing amphetamine and/or methamphetamine. The problem arises because these assays employ a single antiserum or antibody that can recognize both amphetamine and methamphetamine. In order for this antibody to recognize both amphetamine and methamphetamine, it is necessary for it to be capable of recognizing a particular spatial and polar organization common to amphetamine and methamphetamine and to lack specific recognition of those structural features of amphetamine and methamphetamine that are different. Because such an antibody recognizes structural features that are common to both of these compounds but lacks specific recognition of the structural features that are different, it is able to recognize both compounds and the assay will produce a positive result for a sample containing amphetamine and/or methamphetamine. However, antibodies that recognize both compounds have been found to recognize molecules other than amphetamine and methamphetamine that share some but not all of the common spatial and polar features of amphetamine and methamphetamine.
The above problem was solved in U.S. Pat. Nos. 5,135,863 and 5,328,828 (Hu, et al.), which disclose an immunoassay to determine the presence of amphetamines in a sample suspected of containing amphetamine and/or methamphetamine by employing four primary reagents. Two of these reagents are two conjugates, each comprised of a functionally similar label bound to an amphetamine analog and a methamphetamine analog, respectively. The other two reagents are an antibody to amphetamine and an antibody to methamphetamine.
There is, however, a need for assays for the detection of amphetamine and/or methamphetamine where the number of reagents employed is reduced from that mentioned above and the assay maintains the same level of sensitivity, specificity, speed and accuracy as the assay disclosed in U.S. Pat. Nos. 5,135,863 and 5,328,828 utilizing four reagents.